Angular resolution study of GLD Calorimeter 2006/Dec/21 ILC-sousei Annual Meeting M1 ICEPP, Tokyo Hitoshi HANO

Motivation Measurement of the direction of non-pointing photon is important for GMSB (gauge mediated supersymmetry breaking) scenarios. To identify a non-pointing photon, we have to need to measure angular resolution of this Detector (Calorimeter). We have studied using full-simulator (Jupiter) [m] decay length : IP ECAL

GLD detector can be changed !! GLD detector has large-radius and fine-segmented EM Calorimeter. Calorimeter cell size 0.5~10 [cm] It’s very important for cost performance. R [m]Z [m] ECAL Structure W/Scinti./gap 3/2/1(mm) x 33 layers X0X0 26 ECAL geometry in Jupiter ： (barrel) (endcap)

θ, φ resolution study of cluster 1. Shoot Single-gamma from IP with random direction 2. Clustering - use hit data from ECAL(,HCAL) 3. Search central point of cluster 4. Find θ, φ of a central point 5. Compare with MC truth θ （ φ ） resolution [rad] = θ （ φ ） MC – θ （ φ ） meas IP central point γ

Clustering 1. Find the highest energy deposit cell 2. Make a cone with centering around it 3. Define cells which are inside of a cone as one cluster 4. Find a central point by energy weighted mean clustering angle = 10° IP Judging by inner product IP

1cell ( 1cm x 1cm ) θ, φ z=0 ( |cos(θ)|=0 ) max θ 1cell 210cm IP 1cm θ （ φ ） 1cell = 1/210 ≒ 4.7 [mrad] z=280 ( |cos(θ)|=0.8 ) min θ 1cell IP θ 1cell ≒ 1.71 [mrad]

event (random direction) θ resolution meansigma |cos(θ MC )| mean [rad] sigma [rad]

event (random direction) φ resolution meansigma mean [rad] |cos(θ MC )| sigma [rad]

Result (θ, φ resolution) θ,φ resolution θ barrel ： 0.430±0.004 [mrad] θ endcap ： 0.282±0.006 [mrad] φ barrel ： 0.423±0.004 [mrad] φ endcap ： 0.699±0.014 [mrad] θ 1cell ≒ 1.71 ～ 4.70 [mrad] Angular resolution is good as well as cell size (1x1cm)

1. Clustering 2. Find a central point of each layer by energy weighted mean 3. Fit each point with least-square method 4. Find an angle between IP and reconstructed line Angular resolution study of reconstructed line IP γ reconstructed line

Fitting method Find a central point of each layer by energy weighted mean x y weighted by energy deposit Fitting 2-dimentions (x-y) y’ z Fitting new 2-dimentions (y’-z) Distance[cm]

2-dimension normal distribution r histogram F(r)

Distance (d) and angle angle [rad] = d/r fitting function IP central point of cluster r d rd γ reconstructed line

Linearity(1,2,5,10,50 GeV) dependence with cell size 2x2 cm 1x1 cm

Angular resolution dependence with cell size 1 [cm] ： ± 0.29 [mrad] 0.5 [cm] ： ± 0.29 [mrad]

Linearity  LDC : 55mrad/√(E/GeV) (by DOD)  GLD : 122mrad/√(E/GeV) Identify ( 1x1[cm] ) Summary σ= 48.26±0.29[mrad] 3σ= 144 [mrad] IP ECAL We can identify non-pointing photon !! θ> 144 [mrad] (3σ) θ cell size [cm] 0.5x0.5 1x1